In the ordinary situation the two identical reactive groups of a bifunctional reactant are equally reactive. That is, they each will partake in a given reaction with the result that each is converted to something else. If the bifunctional reactant is symmetrical then the product of a reaction involving that reactant likewise will be symmetrical. For this reason the preparation of asymmetrical compounds, especially higher molecular weight compounds, frequently is difficult and correspondingly expensive.
U.S. Pat. No. 3,358,004 (Bliss et al.) shows the preparation of symmetrical azides having the following general formula: ##STR1## where x is oxygen or sulfur and n is an integer of 0 or 1. Such azides are prepared by reaction of an alkali metal azide with the corresponding 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, or dioxide or disulfide thereof. In each case, however, the reactants and products are symmetrical.
Derwent Japanese Patent Report, 4 (37) 5: 13 (Oct. 20, 1965) shows the reaction of a compound of the general formula: ##STR2## where "n is not defined", with a substituted or unsubstituted ethylene imine to form the expected symmetrical product.